Portal:Volcanoes

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A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. The process that forms volcanoes is called volcanism.

On Earth, volcanoes are most often found where tectonic plates are diverging or converging, and because most of Earth's plate boundaries are underwater, most volcanoes are found underwater. For example, a mid-ocean ridge, such as the Mid-Atlantic Ridge, has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes can also form where there is stretching and thinning of the crust's plates, such as in the East African Rift and the Wells Gray-Clearwater volcanic field and Rio Grande rift in North America. Volcanism away from plate boundaries has been postulated to arise from upwelling diapirs from the core–mantle boundary, 3,000 kilometers (1,900 mi) deep within Earth. This results in hotspot volcanism, of which the Hawaiian hotspot is an example. Volcanoes are usually not created where two tectonic plates slide past one another.

Large eruptions can affect atmospheric temperature as ash and droplets of sulfuric acid obscure the Sun and cool Earth's troposphere. Historically, large volcanic eruptions have been followed by volcanic winters which have caused catastrophic famines.

Other planets besides Earth have volcanoes. For example, volcanoes are very numerous on Venus. In 2009, a paper was published suggesting a new definition for the word 'volcano' that includes processes such as cryovolcanism. It suggested that a volcano be defined as 'an opening on a planet or moon's surface from which magma, as defined for that body, and/or magmatic gas is erupted.'

This article mainly covers volcanoes on Earth. See § Volcanoes on other celestial bodies and cryovolcano for more information. (Full article...)

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The geology of the Lassen volcanic area presents a record of sedimentation and volcanic activity in the area in and around Lassen Volcanic National Park in Northern California, U.S.. The park is located in the southernmost part of the Cascade Mountain Range in the Pacific Northwest region of the United States. Oceanic tectonic plates have plunged below the North American Plate in this part of North America for hundreds of millions of years. Heat from these subducting plates have fed scores of volcanoes in California, Oregon, Washington and British Columbia over at least the past 30 million years (see Geology of the Pacific Northwest) and is also responsible for activities in the Lassen volcanic area. Between 3 and 4 million years ago, volcanic-derived mud flows called lahars streamed down several major mountains that included nearby but now extinct Mount Yana and Mount Maidu to become the Tuscan Formation. Basaltic and later andesitic to dacitic flows of lava covered increasingly larger areas of this formation to eventually form the lava plateau that the park sits on. About 600,000 years ago, Mount Tehama started to rise as a stratovolcano in the southwestern corner of the park, eventually reaching an estimated 11,000 feet (3,350 m) in height. Following a series of eruptions approximately 350,000 years ago, its cone collapsed into itself to form a two-mile (3 km) wide caldera.

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Dr. Rosaly M. C. Lopes is a prominent planetary geologist, volcanologist, the author of numerous scientific papers and several books, as well as a great proponent of education. Her major research interests are in planetary and terrestrial surface processes with an emphasis on volcanology.

Lopes was (born January 1957 in Rio de Janeiro, Brazil), where she lived near the famous Ipanema beach. She moved to London, England, in 1975 to study astronomy at the University of London, from where she graduated with honors in astronomy in 1978. For her doctoral studies, she specialized in planetary geology and volcanology and completed her Ph.D. in Planetary Science in 1986 with a thesis on comparing volcanic processes on Earth and Mars. During her Ph.D. she traveled extensively to active volcanoes, particularly Mount Etna in Sicily, and became a member of the UK's Volcanic Eruption Surveillance Team.

She joined JPL as National Research Council Resident Research Associate in 1989 and, after 2 years, became a member of the Galileo Flight project. Lopes worked on the Near Infra-red Mapping Spectrometer (NIMS) team planning and analyzing of observations of Jupiter's volcanic moon Io from 1996 to 2001, during which time she discovered 71 volcanoes on Io that had never before been detected as active. In 2002, Lopes became Investigation Scientist on the Cassini RADAR Team. She has participated on several studies of future NASA and ESA missions as a member of the science definition team, including missions to Saturn and Titan.

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Did you know

... that the volcanic chain (pictured) responsible for creating the island of Hawaii extends all the way to the Kuril–Kamchatka Trench, at the border of Russia?
... that Nintoku Seamount, an underwater volcano in the Hawaiian–Emperor seamount chain, is over 56.2 million years old?
... that volcanoes in the Puyehue Volcano complex may have produced some of the most primitive magmas in the Andes?
... that Pilot Rock is one of the oldest volcanic formations in the Cascade Range?
... that one of a series of hotels called the Volcano House, built at the edge of Kīlauea volcano since 1846, burned to the ground from a kitchen fire?
... that the eruption of Amak Volcano in about 2550 BCE was confirmed by tephrochronology?
... that the Bobrof Volcano is an uninhabited island in the Andreanof Islands, part of Alaska's Aleutian archipelago?
... that the closest transportation to Davidof Volcano is 199 miles (320 km) away in Adak, Alaska?

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Credit: Jan-Pieter Nap

Semeru is the tallest mountain on the island of Java and one of its most active volcanoes. Known also as Mahameru (Great Mountain), it is very steep and rises abruptly above the coastal plains of eastern Java. Maars containing crater lakes have formed along a line through the summit. Semeru lies at the south end of the Tengger Volcanic Complex.

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Now an extinct volcano is not quite so safe a neighbour as many may suppose. Vesuvius was an extinct volcano from time immemorial till the year 63, when it suddenly broke out again, and soon after destroyed Pompeii and Herculaneum; since which time it has never again subsided into entire inactivity.
— A possible event — dangers of our planet, The National Magazine, November 1854, p. 435

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